1. Field of the Invention
The present invention relates to an information record medium such as an optical disk of a high recording density type, which is capable of recording information such as video information, audio information and the like at a high density, and which is represented by a DVD (Digital Video or Versatile Disk). The present invention also relates to a recording apparatus for recording the information onto the information record medium.
2. Description of the Related Art
Conventionally, a so-called LD (Laser Disk) and a so-called CD (Compact Disk) are generalized as optical disks, on which information such as video information, audio information and the like is recorded.
On the LD or the like, the video information and the audio information are recorded together with time information indicating a time at which each information is to be reproduced with respect to a reproduction start position, which each LD or the like has, as a standard position. Thus, other than a general normal reproduction to reproduce the recorded information in the order of recording, various special reproductions are possible, such as a reproduction to extract and listen to an only desirable music out of a plurality of recorded music, a reproduction to listen to the recorded music in a random order and soon, in case of the CD, for example.
However, there is a problem that, according to the above mentioned LD or the like, a so-called interactive and variegated reproduction is not possible in which the audience can have a plurality of selection branches as for the video or audio information to be displayed or sound-outputted and in which the audience can select them to watch or listen to it.
More specifically, when watching and listening are directed to a foreign movie recorded on an LD, it is impossible to select a language used in a superimposed dialogue displayed on a screen (for example, to select superimposed dialogues in both of the Japanese and original languages) to display them on a screen, or when listening is directed to music recorded on a CD, it is impossible to select a kind of sound or voice in the music (for example, to make alternate selection of lyrics in English language version and Japanese language version for listening).
There have recently been made extensive proposals and development of a DVD as an optical disk having an increased storing capacity by about ten times without modification in its own size in comparison with the aforementioned conventional CD. Such a DVD has been schemed out as having a disk structure comprising two recording layers in order to increase the recording capacity thereof.
In the optical disk having such a double-layer structure, it is necessary to adjust a focal distance of an optical pickup and search an address to be reproduced after the adjustment thereof, when switching the recording layer being in reproduction condition to another recording layer during reproduction. A certain period of time is however required for the aforementioned adjustment of the focal distance and the aforementioned search of the address, thus making it hard to reproduce video information and/or audio information without interruption (in seamless reproduction) in case of continuous data. In view of this case, it is possible to extremely increase a capacity of a track buffer of a reproduction apparatus, or decrease a reproduction velocity thus leading to deterioration of video and audio quality, so as to carry out seamless reproduction. However, the former countermeasure leads to an increase in the production cost of the recording apparatus, and the latter countermeasure is unfavorable for a user.